This invention relates to an ink tank for an ink jet printhead.
Ink jet printheads include an ink tank (reservoir), some form of pressure regulator, an ejector chip (such as a heater chip) with nozzle plate, a filter, and ink passages to carry ink from the ink reservoir to the ejector chip. The ejector chip jets the ink out through the nozzle plate. The ink reservoir can be integral with the printhead or can be a separate, removable tank. A printhead with ink reservoirs contained in separate, removable tanks should be able to continue operating after the tank is removed and replaced. When a tank is removed, air can be drawn into the printhead and can cause some or all of the ink ejection nozzles to be starved of ink, which can cause print defects. Additionally, in a replaceable tank system the ink ejector chip may fill with air if the tank is run too low.
In order for the ink ejector chip to eject ink droplets, ink must be present in or at the chip. If air is present in the ink ejector chip, the chip may not effectively eject droplets and may not effectively draw ink from the tank or reservoir. It is therefore often necessary to purge the air from the printhead after a new tank is installed. This process is referred to as retiring the printhead. The present invention provides an apparatus that reprimes the printhead when a new tank is installed.